This invention relates to a process of manufacturing a corner assembly for a vehicle with a wheel hub to maintain a rotor in perpendicular alignment with the axis of the wheel hub.
In vehicles currently manufactured, it is not uncommon for disc brakes to be installed on all four corners of the vehicle wherein a rotor is rotated by a corresponding wheel on the vehicle. The wheel is mounted on a hub that is retained in a bearing that is fixed to a support member secured to the frame of the vehicle. A brake application is effected by moving first and second friction pads retained in a caliper member into engagement with opposing first and second surfaces on the rotor. In disc brake systems, it is important that the first and second friction pads and the rotor are maintained in a perpendicular relationship otherwise during a revolution of rotation of a rotor the clearance, commonly referred to as xe2x80x9clateral runoutxe2x80x9d, between the first and second friction pads can vary and adversely effect a smooth brake application. The effect of lateral runout is sensed by an operator as a surging action or movement on a brake pedal.
In an effort to maintain and effect a perpendicular relationship between a wheel hub and brake components, U.S. Pat. No. 5,842,388 disclosed a process of conjugate machining a rotor and a wheel hub. This process functions in an adequate manner for original equipment that are installed in the manufacture of a new vehicle, unfortunately wear conditions may make it necessary to replace the rotor. Thereafter, when an original rotor is replaced with a new rotor manufacturing tolerances may be cumulative and result in a stack up of tolerances such that an unacceptable xe2x80x9clateral runoutxe2x80x9d may occur with a mixture of new and old components in a disc brake.
In investigating xe2x80x9clateral runoutxe2x80x9d is was perceived that when lug bolts are pressed into pre-drilled openings in a wheel hub some distortion occurs in the material surrounding the openings in wheel rotor. Unfortunately the distortion of each individual opening is different and as a result when a new rotor is mounted on an old wheel hub even though within manufacturing tolerances a particular disc brake assembly for a corner assembly may not be acceptable with respect to lateral runout.
A primary object of the present invention is to provide a process of manufacturing a corner assembly for a vehicle wherein lateral run out between first and second friction faces and a rotor is minimized and at an acceptable level for a brake system whether the rotor is initially installed on a wheel hub by a manufacturer or later replaced with a different rotor by an owner.
According to this process, a wheel hub is selected from a source that has a cylindrical body with a first end and a second end, an axial bore that extends there through, a radially extending mounting flange that is located between the first end and the second end and a plurality of axial openings with a first diameter located at a fixed radial distance from the axis of the axial bore. The wheel hub is placed in an arbor and rotated to partially finish the cylindrical body to define a journal section that extend from the second end toward the mounting flange while the mounting flange is finished to define an inboard face toward the journal section and an out board face toward the first end and machine a radial groove in the out board face of the mounting flange that has a width greater than the diameter of the axial openings. The partially finished wheel hub is removed from the arbor and a bolt is pressed into each of the plurality of axial openings in the flange of the wheel hub to bring a head thereon into engagement with the inboard face of the mounting flange. Thereafter, the wheel hub with the bolts attached thereto is returned to the arbor and rotated to complete the finishing of the wheel hub by machining material therefrom to define: a wheel pilot surface adjacent the first end; a rotor pilot surface adjacent the wheel pilot surface; a bearing surface in the journal section; a first radial face that extends from the rotor pilot surface to the radial groove; and a second radial face that extends from the radial groove to a peripheral surface on outboard surface of the mounting flange to define a hub assembly. The hub assembly is characterized in that the defined wheel pilot surface, rotor pilot surface and bearing surface are concentric to the axial bore of the wheel hub while the first and second radial faces are perpendicular to the axial bore. The hub assembly is thereafter pressed into a bearing retained in a support member that is designed to be fixed to a vehicle. Subsequently, a first rotor is obtained from a source and defined by a second plurality of openings that are located adjacent an inner peripheral surface and first and second opposing friction surfaces located adjacent an outer peripheral surface. The inner peripheral surface of the rotor is located on the rotor pilot surface such that the plurality of bolts correspondingly extend through the second plurality of openings. Later a wheel obtained from a source and defined by a center opening is located on the wheel pilot such that the plurality of bolts extend through a corresponding third plurality of openings in the wheel. When a nut is attached to each bolt of the plurality of bolts an alignment surface on the first rotor is brought into engagement with the first and second radial faces on outboard face of the mounting flange to align the first and second opposing friction surfaces on the rotor in a plane perpendicular to the axis of the hub assembly to define a corner assembly. Prior to the attachment of the wheel to the corner assembly, the wheel hub and knuckle are evaluated by measuring the perpendicular alignment of the first and second opposing friction surfaces of a rotor with respect to the axis of the hub assembly through a gaging operation. The gaging measures expected lateral change in the rotor with respect to the first and second friction surfaces during a revolution of rotation of the rotor. If a gaged lateral change is less that 0.06 mm the corner assembly is accepted and if greater than 0.06 mm the corner assembly is initially rejected. After an initial rejection of a corner assembly resulting from excessive lateral runout, rather that discard the corner assembly, the first rotor is removed from the wheel hub and rotated such that the plurality of bolts are located in different openings to complete a re-assembly of the corner assembly. The re-assembled corner assembly is again reevaluated by rotating the wheel hub repeating the gaging measurement of expected lateral movement of the first and second friction surfaces and the rotor. If the lateral change of the re-assembled corner assembly is less than 0.06 mm the corner assembly is now accepted and it if more than 0.06 mm the corner assembly is finally rejected. After a final rejection of this re-assembled corner assembly, the first rotor is removed from the hub assembly and a second rotor is obtained from the source. The second rotor is placed on the wheel hub and the wheel reattached to the wheel hub to complete a second re-assembly of the corner assembly. The wheel hub is rotating and the gaging measurement is taken to determine its lateral change. If the lateral change is less that 0.06 mm this second re-assembled corner assembly is accepted, however it the change is more that 0.06 mm it is assumed that the tolerance stack up of the components contributes to a lateral runout that is unacceptable for a corner assembly.
An advantage of this invention resides in a process of manufacturing a wheel hub for a corner assembly wherein compatibility with a rotor is enhanced to achieve minimal lateral runout between when an initial rotor in a disc brake is replaced with a second rotor.
A further advantage of this invention resides in a process of partially finishing a wheel hub and installing mounting studs on a flange before finally finishing the surfaces thereon to achieve a perpendicular relationship between a bearing journal, wheel pilot surface, rotor pilot surface and a outboard face on a mounting flange.